Henry Law Calculator
Henry law captures one of the most useful relationships in physical chemistry: how much of a gas dissolves in a liquid depends directly on how hard that gas is pressing down on the surface. At a fixed temperature, the dissolved concentration is proportional to the partial pressure of the gas, so raising the pressure forces more gas into solution and lowering it lets gas escape. It is the law behind the fizz of a soda when you crack the cap, the way oxygen enters the bloodstream in the lungs, and the carbon dioxide that natural waters absorb from the air. This calculator applies the solubility form of the law. Enter the Henry constant for your gas, liquid and temperature, in moles per liter per atmosphere, and the partial pressure of the gas in atmospheres, and the tool returns the equilibrium dissolved concentration in moles per liter. Because the constant is temperature-specific, make sure it matches your conditions, since solubility drops as the liquid warms. Dissolved-gas concentrations are often small, so the tool shows very small nonzero values in scientific notation rather than rounding them to zero. A worked example below reconciles exactly to the calculator.
Henry law makes dissolved concentration proportional to partial pressure: C = k x P. With a Henry constant of 0.034 mol/(L atm) for carbon dioxide at a partial pressure of 1.0 atm, the dissolved concentration is 0.0340 mol/L.
Henry law formula
C = k x P
C = dissolved concentration (mol/L)
k = Henry constant (mol/(L atm))
P = partial pressure of the gas (atm)
The dissolved concentration rises in direct proportion to the partial pressure. The Henry constant sets the slope of that line for a specific gas, liquid and temperature.
Worked example
Carbon dioxide with a Henry constant of 0.034 mol/(L atm), at a partial pressure of 1.0 atm.
- C = k x P.
- C = 0.034 x 1.0.
- C = 0.0340 mol/L.
These are the calculator's default inputs, so the result above matches the widget exactly.
Henry law calculator: frequently asked questions
What does Henry law state?
Henry law states that the amount of a gas that dissolves in a liquid at a given temperature is directly proportional to the partial pressure of that gas above the liquid. Double the pressure and you double the dissolved concentration, as long as the temperature and the gas-liquid pair stay the same.
What is the Henry constant?
The Henry constant, often written k, is the proportionality factor between dissolved concentration and partial pressure for a specific gas, liquid and temperature. In the solubility form used here it has units of moles per liter per atmosphere, so multiplying it by a pressure in atmospheres gives concentration in moles per liter.
Why does carbonated drink fizz when opened?
A sealed carbonated drink holds a high partial pressure of carbon dioxide, so by Henry law a lot of gas stays dissolved. Opening it drops the pressure to atmospheric, the equilibrium concentration falls, and the excess carbon dioxide escapes as bubbles. The same law explains gas exchange in the lungs and in natural waters.
How does temperature affect solubility?
Gas solubility falls as temperature rises, because warmer molecules escape the liquid more easily. The Henry constant is therefore temperature-specific. This calculator uses the constant you supply, so make sure it matches the temperature of your system for an accurate result.
What is the Henry law formula?
Concentration equals the Henry constant times the partial pressure, written C equals k times P. C is the dissolved concentration in moles per liter, k is the Henry constant in moles per liter per atmosphere, and P is the partial pressure of the gas in atmospheres.
Official sources
- Solubility data, Henry constants and chemical reference values: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.